Heat exchanger



H. BONNAUD l-IEAT EXCHANGER June 23, 1953 2 Sheets-Sheet l fig] FiledDec. 31, 1948 HENRI BONNAUD,

V Attorneys June 23, 1953 H. BONNAUD 2,643,100

HEAT EXCHANGER Filed Dec. 51, 1948 2 Sheets-Sheet 2 INVENTORI HENRIBONNAUD,

BY W

TTORNEYS Patented June 2 3,

HEAT EXCHANGER Henri Bonnaud, Virofiay, France, assignor to LAirLiquide, Societe Anonyme pour lEtude et lExploitation des ProcedesGeorges Claude, a company Application December 31, 1948, Serial No.68.561 v In France January 22, 1948 My invention relates toheat-exchangers comprising a casing and a nest, of tubes mounted betweentwo tube-plates fastened to a casing, and specially to heat exchangersin which the tubes are substantially straight and close to one another,as are used, for example, in heat exchangers for the treatment of gasesat low temperatures.

The fastening, employed by me, ensures a more certain air-tightness thanwould be the case where use is made of a sliding joint between thecasing and one of the tube-plates. In the case where a sliding joint isnot employed, heavy strains result when the expansion coeflicient of thetubes is different from that'of the casing. Particularly is this truewhen, during the op= eration of the exchanger, that one of these formerparts: nest of tubes and easing, the coefileient of expansion of whichis the greater, attains a temperature farther from that at which theexchanger has been built and assembled, than the other, as for example,in heat-exchangers utilized for the manufacture of oxygen the airdistillation process. In such exchangers, the tubes, which are braced bybafiies for the circulation of the outside fluid, are generally made ofcopper and contain the cooler of the two fluids between which theheat-exchange takes place. Also, in such exchangers, the casing is madeof steel and, when operating, the casing shrinks less than the tubes fortwo reasons; firstly because the expansion coefficient of steel issmaller than that of copperand secondly, because the casing is incontact with the less cool of the two fluids.

A known expedient for lessening the strains in a tube is to give thetube one or more strong waves, so as to impart to it elasticity enoughfor the strains to remain under the elastic limit of the metal it ismade of. This expedient, however, results in a greater manufacturingcost and in a big increase of the bulk of each tube.

One object of my invention is to provide a heat exohanger of relativelysmall bulk and low cost.

A further object of my invention is to provide a heat-exchanger of longlife and lasting airtightness.

A still further object of my invention is to provide a heat-exchanger inwhich each tube, substantially straight and placed very close to theneighbouring tubes,,is given at least one bow, the deflection of whichis substantially included between 3 and 10 centimetres, this de- 1Claim. (Cl. 257-224) fiection being headed in a way substantiallyparallel to the tangent to the line of drilling of the tube,at the spotwhere the tube in question is fastened to the tube-plate, the bows ofthe tubes being headed in an opposite direction when passing from onerow of tubes, corresponding to one same line of drilling, to theneghbouring row, corresponding to the neighbouring line of drilling, themetal of the tubes working, when the exchanger is operating, at rates ofwhich the maximum is over the elastic'limit of the metal at thetemperature to which it is then brought.

Preferably, each bow is approximately sinusoidal in form and the lengthof its chord is comprised between 4 and 8 times the deflection of thebow.

These and other objects of my invention will become more apparentfromthe following detailed description of a preferred embodiment thereofwhen read in connection with theaccompanying drawings, in which:

Figure l is a side elevational view of the upper end of a vertical nestof tubes according to my invention, "seen from a direction a littlebelowthe horizontal; a portion of the parts is broken off and the casingis not represented, in order to allow what is behind to be seen. j

Figure 2 is a half-section of the casing and of the nest of tubesthrough a horizontal plane passing through themiddle line of the bracingspacing-piece 4.

Figure 3 is-a longitudinal section, through the plane 33 of Figure 2.

The heat exchanger comprises chiefly a casing 6, tubes 2!], 2|, 22,etc., I0, ll, l2, l3, l4, etc. and two tube plates 3, l. The less coolof the two fluids flows inside the casing, outside the tubes; it entersthrough the inlet pipe 58 and leaves through the outlet pipe [1. Theother fluid enters through pipe I6, flows inside the tubes, and leavesthrough pipe I9.

In the tube-plate 3, are expanded the tubes Ml, ll, i2, i3, etc., 29,2|, 22, 23, etc. in which circulates the cooler fluid. The tubes 20, 2!,

etc. fastened to the tube-plate along the same returning to thesurrounding temperature. 'Theprecaution has been taken, besides, ofproviding tubes that are slightly too longg'so-as to compress them onassembly, the effect 01,. which is to lessen the elongation strain towhich they are'subjected when they enclose the cooler liquid. Thesmallness of the deflection lessens the cost or bowing the tubes andassembling the exchanger, and re duces the space occupied by the tubes..The bow deflection of the tube [4, for instance. extends al n a l nesubstantially parallel te'the ang n at the centre M cif h hole or thetuh elate 3 where is eXPandedthiS, tuhe. l4. t9 he ine f; d l g f th tues of the same rewr het s o say .anieen ial to the circle p ss,- inghrquweh e simila centr s 0;, it"... tc- 1 the hQ es iqrth ub s 1 e. s merow; h p iph r es oi the h l s ins ew ieh. h tubes are. pen ed'are indea ed i r k line 'on Fig. 2 o he "a conc ed. y he o s o the neighbouringtubes. relation to the axis or the exchanger; the deflection of thebowingis headed in one direction forall'the tubes of this row and in theopposite direction for all the tubes of the neighbouring row 01: rows.

The bowed length oi the, tubes is short relatively'to the total lengththereof. This allows perforated baffles such as 26, 21,38 to be threadythetub s a d, plac d. in. po o s onvenient or i ng he fle ft a ui whichs around the. tubes.

On the figures are s o n. metal spacing strips sue the on wit he e r ncnum er 4'. 'Ijhese strips are inserted between neighbouring rows oi tuhl are. pos tio ed along bowed p rts. of he t b s; and a e fixed in.their Dosii n by we d ng sev ral points, thereof, to. adiacent tubes.

I View th fore oing. description of a prei re embod ment or my'inr'en 'tit will. nowh appa eht th tthe hea rxchang rsh wn has many advantagesover devices now inuse It. is air; tight. and it may be, subiected, agreat. number 01' times to cooling to working temperature and heating toambient temperature before breaking and, moreover, it is easy tomanufacture and its bulk is substantially the same as that of exchangerswith rectilinear tubes.

While Ihaveshown and described a preferred embodiment of my invention,it will be understood that changes and modifications may be made thereinwithout departing from the prin-- ciples thereof.

What I claim is:

A heat exchanger, comprising a casing, two spaced tube-plates enclosedin said casing and fastenedthereto, a nest of metal tubes arranged inrows and mounted between said tube-plates, inlet and outlet pipesconnected to said casing for a heat-exchangemedium intended to circulatein said casing and inlet and outlet pipes connected to said tube-platesfor another heat-exchange medium intended to circulate in said tubesithe linear expansion coeificient of the metal of the tubes beingdifierent from that of the casing, eachftube being substantiallystraight and having: at least one bow. the deflection of said how being.substantially directed according to the direction. of therow of. saidtubes in the neighborhood or said bow, the bows of the tubes beingheaded in an opposite direction when passing from. one row oi tubes tothe neighboring row, the chord subtending 'said bow being between 4 and,8 times the deflection of said bow, said deflection being greater than 3centimetres and smaller than, '10 centimetres,, the bowed portion of thetube extending over less than half the Iength of said'tube andthe'non-bowed portion being practically directed according to thestraight line, joining the places where said tube is mounted'inthetube-piates, whereby when said heat exchanger isemployed ina. heatexchange process, each tube willwork above the elastic limit oi themetal thereof at the temperature prevailing during said'heat exchangeprocess.

' HENRI BONNAUD.v

References Cited inthe file of; this patent UNITED STATES. PATENTSNumber Name: Date:

136333, Wheelock; Jan. 30, 1874 1,125,758, Stack; Jan. 19,, 1915 15481.49; Muh-leisen' Feb. 25, 1930 1.975476% Harter- Oct, 9 193.42,241,186; Coons May 6-. 1941 2,431,630 Arveson Nov. 25, 1947

